Intelligent read strategy within a dispersed storage network (dsn)

ABSTRACT

A computing device includes an interface configured to interface and communicate with a dispersed storage network (DSN), a memory that stores operational instructions, and a processing module operably coupled to the interface and memory such that the processing module, when operable within the computing device based on the operational instructions, is configured to perform various operations. For example, the computing device generates and transmits a read request for a set of encoded data slices (EDSs) of a data object to primary storage units (SUs). The data object is stored within primary and secondary SUs. The computing device then receives at least the read threshold number of EDSs from the plurality of primary SUs. The primary SUs operate selectively to provide the at least the read threshold number of EDSs to the computing device either from memory of primary SU(s) or from secondary SU(s).

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. § 120 as a continuation of U.S. Utility application Ser. No.15/249,187, entitled “INTELLIGENT READ STRATEGY WITHIN A DISPERSEDSTORAGE NETWORK (DSN),” filed Aug. 26, 2016, pending, which claimspriority pursuant to 35 U.S.C. § 119(e) to U.S. Provisional PatentApplication Ser. No. 62/211,975, entitled “STORING ENCODED DATA SLICESIN A DISPERSED STORAGE NETWORK,” filed Aug. 31, 2015, expired, both ofwhich are hereby incorporated herein by reference in their entirety andmade part of the present U.S. Utility Patent Application for allpurposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

Retrieval of stored data within data storage systems can operatesub-optimally for many reasons. For example, depending of the type ofdata that is stored and where the data is stored, retrieval of the datamay be slowed when operation of a communication network connectingvarious devices of a data storage system is slowed. Moreover, when thecommunication network is experiences interference, noise, problems, etc.some of the data may be returned corrupted, unusable, or unrecoverablein response to a request for the data. The prior art does not provide anadequate means to deal with such situations while maintaining a highlevel of performance for the overall data storage system.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9A is a schematic block diagram of another embodiment of adispersed storage network (DSN) in accordance with the presentinvention;

FIG. 9B is a schematic block diagram of another embodiment of adispersed storage network (DSN) in accordance with the presentinvention;

FIG. 9C is a schematic block diagram of an example of various parametersassociated with a set of encoded data slices (EDSs) stored withinstorage units (SUs) in accordance with the present invention

FIG. 10A is a diagram illustrating an embodiment of a method forexecution by one or more computing devices in accordance with thepresent invention; and

FIG. 10B is a diagram illustrating another embodiment of a method forexecution by one or more computing devices in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2, or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 & 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data as subsequently described with reference to oneor more of FIGS. 3-8. In this example embodiment, computing device 16functions as a dispersed storage processing agent for computing device14. In this role, computing device 16 dispersed storage error encodesand decodes data on behalf of computing device 14. With the use ofdispersed storage error encoding and decoding, the DSN 10 is tolerant ofa significant number of storage unit failures (the number of failures isbased on parameters of the dispersed storage error encoding function)without loss of data and without the need for a redundant or backupcopies of the data. Further, the DSN 10 stores data for an indefiniteperiod of time without data loss and in a secure manner (e.g., thesystem is very resistant to unauthorized attempts at accessing thedata).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSN memory 22 fora user device, a group of devices, or for public access and establishesper vault dispersed storage (DS) error encoding parameters for a vault.The managing unit 18 facilitates storage of DS error encoding parametersfor each vault by updating registry information of the DSN 10, where theregistry information may be stored in the DSN memory 22, a computingdevice 12-16, the managing unit 18, and/or the integrity processing unit20.

The DSN managing unit 18 creates and stores user profile information(e.g., an access control list (ACL)) in local memory and/or withinmemory of the DSN module 22. The user profile information includesauthentication information, permissions, and/or the security parameters.The security parameters may include encryption/decryption scheme, one ormore encryption keys, key generation scheme, and/or dataencoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particularuser, a user group, a vault access, public vault access, etc. Forinstance, the DSN managing unit 18 tracks the number of times a useraccesses a non-public vault and/or public vaults, which can be used togenerate a per-access billing information. In another instance, the DSNmanaging unit 18 tracks the amount of data stored and/or retrieved by auser device and/or a user group, which can be used to generate aper-data-amount billing information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an 10 interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1. Note that the 10 deviceinterface module 62 and/or the memory interface modules 66-76 may becollectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3, the computing device also createsa slice name (SN) for each encoded data slice (EDS) in the set ofencoded data slices. A typical format for a slice name 60 is shown inFIG. 6. As shown, the slice name (SN) 60 includes a pillar number of theencoded data slice (e.g., one of 1-T), a data segment number (e.g., oneof 1-Y), a vault identifier (ID), a data object identifier (ID), and mayfurther include revision level information of the encoded data slices.The slice name functions as, at least part of, a DSN address for theencoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4. In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG.8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4. The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

FIG. 9A is a schematic block diagram of another embodiment 901 of adispersed storage network (DSN) in accordance with the presentinvention. This diagram shows a schematic block diagram of anotherembodiment of a dispersed storage network (DSN) that includes primarystorage units (SUs) 910, secondary storage units 920, the network 24 ofFIG. 1, and the DSN processing unit (or computing device) 16 of FIG. 1.The primary SUs 910 includes one or more storage units 1-x. Thesecondary SUs 920 includes one or more storage units 1-y. Each storageunit may be implemented utilizing the DS execution (EX) unit 36 ofFIG. 1. The DSN functions to recover stored data from one or more of theprimary SUs 910 and the secondary SUs 920.

In an example of operation of the recovering of the store data, the DSNprocessing unit (or computing device) 16 issues at least a decodethreshold number of read slice requests to primary SUs 910 whenrecovering a data segment, where the data segment is dispersed storageerror encoded to produce a set of encoded data slices, where at least aninformation dispersal algorithm (IDA) and/or dispersed error encoding(DSE) threshold number of encoded data slices of the set of encoded dataslices are stored in the primary SUs 910, and where the encoded dataslices are stored in the secondary SUs 920 when a storage failure occursof the at least the IDA and/or DSE threshold number of encoded dataslices of the primary SUs 910. For example, the DSN processing unit (orcomputing device) 16 selects and IDA and/or DSE threshold number ofstorage units of the primary SUs 910, generates the IDA and/or DSEthreshold number of read slice requests 1-k, and sends, via the network24, the IDA and/or DSE threshold number of read slice requests 1-k tothe selected primary SUs 910.

Having issued the read slice requests 1-k to the primary SUs 910, theDSN processing unit (or computing device) 16 determines a number ofextra read slice requests to send to the primary SUs 910. The DSNprocessing unit (or computing device) 16 determines the number of extraread slice requests based on one or more of a predetermination, aprevious extra value, an estimated DSN storage reliability level, a DSNperformance level, a DSN resource utilization level, a desired DSNperformance level, and a desired DSN resource utilization level. Forexample, the DSN processing unit (or computing device) 16 determines toraise extra value when the DSN storage reliability level is unfavorable.As another example, the DSN processing unit (or computing device) 16determines to lower the extra value when the DSN resource utilizationlevel is unfavorable.

Having determined the number of extra read slice request, the DSNprocessing unit (or computing device) 16 issues the number of extra readslice requests to the primary SUs 910. For example, the DSN processingunit (or computing device) 16 selects further storage units of theprimary SUs 910, generates the extra number of read slice requests 1-E,and sends, via the network 24, the extra number of extra read slicerequests 1-E to the selected for the storage units of the primary SUs910.

When not receiving at least a decode threshold number of encoded dataslices of the set of encoded data slices via read slice responses 1-kand/or extra read slice responses 1-E from the primary SUs 910, the DSNprocessing unit (or computing device) 16 issues one or more secondaryread slice requests 1-S to the secondary SUs 920. When receiving the atleast a decode threshold number of encoded data slices via one or moreof the read slice responses 1-k, the extra read slice responses 1-E, andsecondary read slice responses 1-S, the DSN processing unit (orcomputing device) 16 dispersed storage error decodes the receivedencoded data slices to reproduce the data segment.

In an example, the DS processing unit (or computing device) 16 is incommunication with a storage set 910 via network 24. The DS processingunit (or computing device) 16 includes an interface configured tointerface and communicate with a dispersed storage network (DSN) thatincludes the storage set 910 (e.g., that may include a number of SUs),memory that stores operational instructions, and a processing moduleoperably coupled to the interface and to the memory, wherein theprocessing module, when operable within the computing device based onthe operational instructions, is configured to perform variousfunctions.

In an example of operation and implementation, the DS processing unit(or computing device) 16 generates a read request for a set of encodeddata slices (EDSs) of a data object that is stored within primarystorage units (SUs) and secondary SUs within the DSN, wherein the readrequest includes a read extra request that specifies more than a readthreshold number of EDSs from the primary SUs and/or instruction to a SUof the primary SUs to forward the read request to at least one SU of thesecondary SUs when a DSN operational characteristic compares unfavorablyto an acceptable DSN operational characteristic as determined by the DSprocessing unit (or computing device) 16.

Note that sets of EDSs of the data object are stored within the primarySUs and the secondary SUs within the DSN. The data object is segmentedinto data segments, and a data segment of the data segments is dispersederror encoded in accordance with dispersed error encoding parameters toproduce the set of EDSs that is of pillar width. The decode thresholdnumber of EDSs are needed to recover the data segment, the readthreshold number of EDSs provides for reconstruction of the datasegment, and a write threshold number of EDSs provides for a successfultransfer of the set of EDSs from a first at least one location in theDSN to a second at least one location in the DSN.

The DS processing unit (or computing device) 16 then transmits the readrequest for the set of EDSs of the data object to the primary SUs withinthe DSN and receives at least the read threshold number of EDSs from theprimary SUs. Also, note that the SU of the primary SUs provides an EDSof the set of EDSs from memory of the SU of the primary SUs when the EDSof the set of EDSs is stored and available within the SU of the primarySUs. In addition, the SU of the primary SUs provides the EDS of the setof EDSs after receipt thereof from a SU of the secondary SUs when atleast one of the DSN operational characteristic compares unfavorably tothe acceptable DSN operational characteristic as determined by the SU ofthe primary SUs or the EDS of the set of EDSs is unavailable within thememory of the SU of the primary SUs. In general, both the DS processingunit (or computing device) 16 and at least one SU of the primary SUsinclude intelligence to determine how, where, and when to providerequested EDSs to a requesting device (e.g., to the DS processing unit(or computing device) 16). In an example, each SU of the primary SUsincluded intelligence to determine whether to forward a read request toat least one SU of the secondary SUs. In addition, the DS processingunit (or computing device) 16 itself may also include intelligence toprovide suggestion, recommendation, instruction, and/or otherinformation to at least one SU of the primary SUs to direct theoperation of the at least one SU of the primary SUs.

In some examples, the DS processing unit (or computing device) 16operates to identify the primary SUs among a plurality of overall SUs ofthe DSN based on an affinity of the primary SUs that specifies anestimated likelihood that the set of EDSs are stored within the primarySUs. In other examples, the DS processing unit (or computing device) 16operates to generate the read request for the set of EDSs of the dataobject to specify instruction for the SU of the primary SUs to generateanother read extra request that specifies the more than the readthreshold number of EDSs based on the read request forwarded from the SUof the primary SUs and to transmit the another read extra request to theat least one SU of the secondary SUs.

In even other examples, the DS processing unit (or computing device) 16operates to generate the read request for the set of EDSs of the dataobject that is stored within the primary SUs and the secondary SUswithin the DSN, wherein the read request specifies no more than the readthreshold number of EDSs when the DSN operational characteristiccompares favorably to the acceptable DSN operational characteristic asdetermined by the computing device and receive the read threshold numberof EDSs from the primary SUs in response to the primary SUs.

In some other examples, the DS processing unit (or computing device) 16operates to instruct at least one SU of the primary SUs to generate atleast one redundant EDS based on at least one EDS of the set of EDSs andto transmit the at least one redundant EDS to the at least one SU of thesecondary SUs for storage therein when the DSN operationalcharacteristic compares unfavorably to the acceptable DSN operationalcharacteristic as determined by the computing device. In even otherexamples, the DS processing unit (or computing device) 16 operates toinstruct at least one SU of the primary SUs to generate a copy of theset of EDSs and to transmit the copy of the set of EDSs to the secondarySUs for storage therein when the DSN operational characteristic comparesunfavorably to the acceptable DSN operational characteristic asdetermined by the computing device.

Note that is some examples the read extra request specifies a firstnumber of EDSs that is more than the read threshold number of EDSs fromthe primary SUs when the DSN operational characteristic comparesunfavorably to the acceptable DSN operational characteristic asdetermined by the computing device within a first unfavorable comparisonrange. Also, the read extra request may also specify a second number ofEDSs that is more than the read threshold number of EDSs from theprimary SUs when the DSN operational characteristic compares unfavorablyto the acceptable DSN operational characteristic as determined by thecomputing device within a second unfavorable comparison range.

Note that the DS processing unit (or computing device) 16 may be locatedat a first premises that is remotely located from at least one SU of theprimary SUs or plurality of secondary SUs the within the DSN. Also, notethat the DS processing unit (or computing device) 16 may be of any of avariety of types of devices as described herein and/or their equivalentsincluding a SU of the primary SUs or the secondary SUs within the DSN, awireless smart phone, a laptop, a tablet, a personal computers (PC), awork station, and/or a video game device. Note also that the DSN may beimplemented to include or be based on any of a number of different typesof communication systems including a wireless communication system, awire lined communication systems, a non-public intranet system, a publicinternet system, a local area network (LAN), and/or a wide area network(WAN).

FIG. 9B is a schematic block diagram of another embodiment 902 of adispersed storage network (DSN) in accordance with the presentinvention. This diagram shows a different configuration by which a DSprocessing unit (or computing device) 16 is in communication withprimary SUs 910 and secondary SUs 920 a (and optionally also secondarySUs 920). For example, the secondary SUs 920 a are shown as beingdirectly connected and/or coupled to the primary SUs 910 without needingto go through the network 24. Note that the optionally includedsecondary SUs 920 may also be in communication with the primary SUs 910via the network 24.

In general, any of a variety of configurations may be used that includeprimary SUs and secondary SUs. The primary SUs and the secondary SUs maybe viewed as being different respective layers of SUs in the DSN fromcertain perspectives. For example, the primary SUs may be configured toaccess the secondary SUs and selectively retrieve EDSs there from basedon processing, decision-making, and intelligence included within theprimary SUs. In addition, the primary SUs may be configured to operatecooperatively with the DS processing unit (or computing device) 16 todetermine how to provide EDSs to the DS processing unit (or computingdevice) 16.

FIG. 9C is a schematic block diagram of an example 903 of variousparameters associated with a set of encoded data slices (EDSs) storedwithin storage units (SUs) in accordance with the present invention.This diagram shows generally the relationship between a pillar widthnumber of SUs (and/or EDSs), a decode threshold number of SUs (and/orEDSs), a read threshold number of SUs (and/or EDSs), and a writethreshold number of SUs (and/or EDSs). When considering such numberswith respect to EDSs, note that a data object is segmented into datasegments, and a data segment of the plurality of data segments isdispersed error encoded in accordance with dispersed error encodingparameters to produce the set of EDSs that is of pillar width. A decodethreshold number of EDSs are needed to recover the data segment, a readthreshold number of EDSs provides for reconstruction of the datasegment, and a write threshold number of EDSs provides for a successfultransfer of the set of EDSs from a first at least one location in theDSN to a second at least one location in the DSN. Note also that theread threshold number and the write threshold number may be the same incertain examples and based on certain dispersed error encodingparameters. In general, the read threshold number is greater than thedecode threshold number. Also, the write threshold number is generallygreater than the read threshold number and less than the pillar width.

A target width that is greater than the pillar width may be used togenerate redundant copies of the EDSs. In one example, a target width 1corresponds to generating redundant copies of EDSs that is fewer thanthe pillar width of EDSs. For example, copies of a subset of the EDSswithin the pillar width number of EDSs are made for use to service theDSN. Alternatively, a target width 2 corresponds to generating aninteger multiple number of redundant copies of those EDSs that arewithin the pillar width of EDSs (e.g., one redundant copy of those EDSs,two redundant copies of those EDSs, three two redundant copies of thoseEDSs, etc.). Note also that any desired values of target width may beadapted, modified, adjusted, etc. to be any of the various numbers asdescribed with respect to this diagram at different times and based ondifferent considerations.

Any desired example of additional EDSs may be generated and storedwithin primary SUs and/or secondary SUs. As desired, any particularconfiguration of redundant and/or additional EDSs may be generated andstored within these primary SUs and/or secondary SUs. In some examples,there may be one or more EDSs of the set of EDSs that is not stored inany SU of the primary SUs, but that EDS or a copy of that EDS will bestored in at least one SU of the secondary SUs. In general, the primarySUs and secondary SUs store EDSs so that a combination of EDSs retrievedthere from may be provided to a requesting device (e.g., a DS processingunit (or computing device) 16) via at least one SU of the primary SUs.In some examples, a SU of the primary SUs receives at least one EDS fromat least one SU of the secondary SUs and provided it/forwards it to therequesting device (e.g., a DS processing unit (or computing device) 16).

FIG. 10A is a diagram illustrating an embodiment of a method 1001 forexecution by one or more computing devices in accordance with thepresent invention. This diagram shows a flowchart illustrating anexample of recovering data. The method begins or continues at a step1010 where a processing module of a distributed storage and task (DS)processing unit issues at least a decode threshold number of read slicerequests to the primary SUs when recovering a data segment. For example,the processing module selects an information dispersal algorithm (IDA)threshold number of SUs of the primary SUs, generates an IDA and/or DSEthreshold number of read slice requests, and sends the IDA and/or DSEthreshold number of read slice requests to the selected primary SUs. Asanother example, the processing module sends a read threshold number ofread slice requests, where the read threshold number is greater than theIDA and/or DSE threshold number.

The method continues at a step 1020 where the processing moduledetermines a number of extra read slice requests to send to the primarySUs. The processing module determines the number of extra read slicerequests based on one or more of a predetermination, a previous extravalue, a dispersed storage network (DSN) estimated storage reliabilitylevel, a DSN performance level, a DSN resource utilization level, adesired DSN performance level, and a desired DSN resource utilizationlevel.

The method continues at a step 1030 where the processing module issuesthe number of actual read slice requests to the primary SUs. The issuingincludes selecting further SUs of the primary SUs, generating the extranumber of read slice requests, and sending the extra number of extraread slice requests to the selected further SUs of the primary SUs.

When not receiving at least a decode threshold number of encoded dataslices from the primary SUs, the method continues at a step 1040 wherethe processing module issues one or more secondary read slice requeststo the secondary SUs. For example, the processing module determines anumber of secondary read slice requests based on a number of requiredencoded data slices to achieve the decode threshold number of encodeddata slices, generates the one or more secondary read slice requests,and sends the secondary read slice requests to the correspondingsecondary SUs. When receiving the at least a decode threshold number ofencoded data slices, the method continues at a step 1050 where theprocessing module dispersed storage error decodes the received encodeddata slices to reproduce the data segment.

FIG. 10B is a diagram illustrating another embodiment of a method 1002for execution by one or more computing devices in accordance with thepresent invention. The method 1002 operates in step 1011 by generating aread request for a set of encoded data slices (EDSs) of a data objectthat is stored within primary storage units (SUs) and secondary SUswithin a dispersed storage network (DSN). Note that the read requestincludes a read extra request that specifies more than a read thresholdnumber of EDSs from the primary SUs and/or instruction to a SU of theprimary SUs to forward the read request to at least one SU of thesecondary SUs when a DSN operational characteristic compares unfavorablyto an acceptable DSN operational characteristic as determined by thecomputing device. Also, note that sets of EDSs of the data object arestored within the primary SUs and the secondary SUs within the DSN. Thedata object is segmented into data segments, and a data segment of thedata segments is dispersed error encoded in accordance with dispersederror encoding parameters to produce the set of EDSs that is of pillarwidth. Also, a decode threshold number of EDSs are needed to recover thedata segment, the read threshold number of EDSs provides forreconstruction of the data segment, and a write threshold number of EDSsprovides for a successful transfer of the set of EDSs from a first atleast one location in the DSN to a second at least one location in theDSN.

The method 1002 then operates in step 1021 by transmitting (e.g., via aninterface of the computing device configured to interface andcommunicate with the DSN) the read request for the set of EDSs of thedata object to the primary SUs within the DSN. The method 1002 thenoperates in step 1031 by receiving (e.g., via the interface of thecomputing device configured to interface and communicate with the DSN)at least the read threshold number of EDSs from the primary SUs.

In some examples, the SU of the primary SUs provides an EDS of the setof EDSs from memory of the SU of the primary SUs when the EDS of the setof EDSs is stored and available within the SU of the primary SUs asshown in step 1041. In addition, the SU of the primary SUs provides theEDS of the set of EDSs after receipt thereof from a SU of the secondarySUs when at least one of the DSN operational characteristic comparesunfavorably to the acceptable DSN operational characteristic asdetermined by the SU of the primary SUs or the EDS of the set of EDSs isunavailable within the memory of the SU of the primary SUs as shown instep 1051.

This disclosure presents various embodiments, examples, etc. that may beused to provide for determining a read strategy to receive at least adecode threshold and/or at least a read threshold number of EDSs toreconstruct a data segment. For example, with respect to a DSN in whichtrimmed writes (e.g., write operations that operates based on fewer thana write threshold number of EDSs) or target width systems (e.g.,including those that may include target widths greater than the pillarwidth such as with respect to FIG. 9C) may operate using a concept ofaffinity. This concept of affinity may be described as referring tothose SUs having some primary SUs that be more likely to contain EDSsthat are being requested than other secondary SUs.

For example, there may be different strategies for reading data from theDSN efficiently. Examples of such strategies may result in differentnumbers of EDSs being returned, depending on the state of the DSN at thetime the data was written, etc. In a first example strategy, the DSprocessing unit issues at least a threshold (e.g., a decode thresholdand/or read threshold) number of reads to a subset of the primary SUs,and then issues reads to all the secondary SUs. In the case that EDSsare properly stored only on the primary SUs, this strategy returns onlyas many EDSs as the number of reads issued to the primary locations (forwhen all EDSs are at the proper locations, every primary SU has an EDSand no secondary SU has an EDS). For each primary SU does not have anEDS, there will be a corresponding secondary SU that does hold an EDS.Therefore, when EDSs are not at their proper locations, the abovestrategy can result in many more EDSs being returned than expected. Analternate strategy is to use “Read Extra” to send some number of readrequests to the primary SUs plus some extra number, also sent to theother primary SUs. This is more likely to return extra EDSs when thingsare healthy (at their proper locations) but can have a lower worst-caseupper bound for the number of EDSs returned. The DS processing unit, mayalternate between these strategies based on recent experience of thenumber of extra EDSs being returned. Depending on how healthy the systemis, one strategy may be preferable compared to the other in that itreturns less EDSs and uses less network IO.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A computing device comprising: an interfaceconfigured to interface and communicate with a dispersed or distributedstorage network (DSN); memory that stores operational instructions; andprocessing circuitry operably coupled to the interface and to thememory, wherein the processing circuitry is configured to execute theoperational instructions to: generate a read request for a set ofencoded data slices (EDSs) of a data object that is distributedly storedwithin a plurality of primary storage units (SUs) and a plurality ofsecondary SUs within the DSN, wherein the read request includes a readextra request that specifies at least one of more than a read thresholdnumber of EDSs from the plurality of primary SUs or instruction to a SUof the plurality of primary SUs to forward the read request to at leastone SU of the plurality of secondary SUs, wherein sets of EDSs of thedata object are distributedly stored within the plurality of primary SUsand the plurality of secondary SUs within the DSN, wherein the dataobject is segmented into a plurality of data segments, wherein a datasegment of the plurality of data segments is dispersed error encoded inaccordance with dispersed error encoding parameters to produce the setof EDSs, wherein the read threshold number of EDSs provides forreconstruction of the data segment; transmit, via the interface and viathe DSN, the read request for the set of EDSs of the data object to theplurality of primary SUs within the DSN; and receive, via the interfaceand via the DSN, at least the read threshold number of EDSs from theplurality of primary SUs, wherein: the SU of the plurality of primarySUs provides an EDS of the set of EDSs to the computing device via theDSN and via the interface after receipt thereof from a SU of theplurality of secondary SUs based on at least one of unfavorablecomparison of a DSN operational characteristic to an acceptable DSNoperational characteristic as determined by the SU of the plurality ofprimary SUs or the EDS of the set of EDSs is unavailable within othermemory of the SU of the plurality of primary SUs.
 2. The computingdevice of claim 1, wherein the processing circuitry is furtherconfigured to execute the operational instructions to: compare the DSNoperational characteristic to the acceptable DSN operationalcharacteristic; and generate the instruction to the SU of the pluralityof primary SUs to forward the read request to at least one SU of theplurality of secondary SUs based on unfavorable comparison of the DSNoperational characteristic compares to the acceptable DSN operationalcharacteristic.
 3. The computing device of claim 1, wherein theprocessing circuitry is further configured to execute the operationalinstructions to: receive, via the interface and via the DSN, the atleast the read threshold number of EDSs from the plurality of primarySUs, wherein the SU of the plurality of primary SUs provides the EDS ofthe set of EDSs from the memory of the SU of the plurality of primarySUs to the computing device via the DSN and via the interface when theEDS of the set of EDSs is stored and available within the SU of theplurality of primary SUs.
 4. The computing device of claim 1, wherein:the read extra request specifies a first number of EDSs that is morethan the read threshold number of EDSs from the plurality of primary SUsbased on unfavorable comparison of the DSN operational characteristic tothe acceptable DSN operational characteristic as determined by thecomputing device within a first unfavorable comparison range; and theread extra request specifies a second number of EDSs that is more thanthe read threshold number of EDSs from the plurality of primary SUsbased on unfavorable comparison the DSN operational characteristic tothe acceptable DSN operational characteristic as determined by thecomputing device within a second unfavorable comparison range.
 5. Thecomputing device of claim 1, wherein the processing circuitry is furtherconfigured to execute the operational instructions to: instruct at leastone SU of the plurality of primary SUs to generate at least oneredundant EDS based on at least one EDS of the set of EDSs and totransmit the at least one redundant EDS to the at least one SU of theplurality of secondary SUs for storage therein based on unfavorablecomparison of the DSN operational characteristic to the acceptable DSNoperational characteristic as determined by the computing device.
 6. Thecomputing device of claim 1, wherein: a decode threshold number of EDSsare needed to recover the data segment; a write threshold number of EDSsprovides for a successful transfer of the set of EDSs from a first atleast one location in the DSN to a second at least one location in theDSN; the set of EDSs is of pillar width and includes a pillar number ofEDSs; each of the decode threshold number, the read threshold number,and the write threshold number is less than the pillar number; and thewrite threshold number is greater than or equal to the read thresholdnumber that is greater than or equal to the decode threshold number. 7.The computing device of claim 1 further comprising: another SU of theplurality of primary SUs or the plurality of secondary SUs within theDSN, a wireless smart phone, a laptop, a tablet, a personal computers(PC), a work station, or a video game device.
 8. The computing device ofclaim 1, wherein the DSN includes at least one of a wirelesscommunication system, a wire lined communication system, a non-publicintranet system, a public internet system, a local area network (LAN),or a wide area network (WAN).
 9. A computing device comprising: aninterface configured to interface and communicate with a dispersed ordistributed storage network (DSN); memory that stores operationalinstructions; and processing circuitry operably coupled to the interfaceand to the memory, wherein the processing circuitry is configured toexecute the operational instructions to: generate a read request for aset of encoded data slices (EDSs) of a data object that is distributedlystored within a plurality of primary storage units (SUs) and a pluralityof secondary SUs within the DSN, wherein the read request includes aread extra request that specifies at least one of more than a readthreshold number of EDSs from the plurality of primary SUs orinstruction to a SU of the plurality of primary SUs to forward the readrequest to at least one SU of the plurality of secondary SUs, whereinsets of EDSs of the data object are distributedly stored within theplurality of primary SUs and the plurality of secondary SUs within theDSN, wherein the data object is segmented into a plurality of datasegments, wherein a data segment of the plurality of data segments isdispersed error encoded in accordance with dispersed error encodingparameters to produce the set of EDSs, wherein the read threshold numberof EDSs provides for reconstruction of the data segment; transmit, viathe interface and via the DSN, the read request for the set of EDSs ofthe data object to the plurality of primary SUs within the DSN; comparea DSN operational characteristic to an acceptable DSN operationalcharacteristic; and receive, via the interface and via the DSN, at leastthe read threshold number of EDSs from the plurality of primary SUs,wherein: the SU of the plurality of primary SUs provides an EDS of theset of EDSs to the computing device via the DSN and via the interfaceafter receipt thereof from a SU of the plurality of secondary SUs basedon at least one of unfavorable comparison of the DSN operationalcharacteristic to the acceptable DSN operational characteristic asdetermined by the SU of the plurality of primary SUs or the EDS of theset of EDSs is unavailable within other memory of the SU of theplurality of primary SUs; and instruct at least one SU of the pluralityof primary SUs to generate at least one redundant EDS based on at leastone EDS of the set of EDSs and to transmit the at least one redundantEDS to the at least one SU of the plurality of secondary SUs for storagetherein based on unfavorable comparison of the DSN operationalcharacteristic to the acceptable DSN operational characteristic asdetermined by the computing device.
 10. The computing device of claim 9,wherein the processing circuitry is further configured to execute theoperational instructions to: generate the instruction to the SU of theplurality of primary SUs to forward the read request to at least one SUof the plurality of secondary SUs based on unfavorable comparison of theDSN operational characteristic compares to the acceptable DSNoperational characteristic.
 11. The computing device of claim 9, whereinthe processing circuitry is further configured to execute theoperational instructions to: receive, via the interface and via the DSN,the at least the read threshold number of EDSs from the plurality ofprimary SUs, wherein the SU of the plurality of primary SUs provides theEDS of the set of EDSs from the other memory of the SU of the pluralityof primary SUs to the computing device via the DSN and via the interfacewhen the EDS of the set of EDSs is stored and available within the SU ofthe plurality of primary SUs.
 12. The computing device of claim 9,wherein: the read extra request specifies a first number of EDSs that ismore than the read threshold number of EDSs from the plurality ofprimary SUs based on unfavorable comparison of the DSN operationalcharacteristic to the acceptable DSN operational characteristic asdetermined by the computing device within a first unfavorable comparisonrange; and the read extra request specifies a second number of EDSs thatis more than the read threshold number of EDSs from the plurality ofprimary SUs based on unfavorable comparison the DSN operationalcharacteristic to the acceptable DSN operational characteristic asdetermined by the computing device within a second unfavorablecomparison range.
 13. The computing device of claim 9, wherein the DSNincludes at least one of a wireless communication system, a wire linedcommunication system, a non-public intranet system, a public internetsystem, a local area network (LAN), or a wide area network (WAN).
 14. Amethod for execution by a computing device, the method comprising:generating a read request for a set of encoded data slices (EDSs) of adata object that is distributedly stored within a plurality of primarystorage units (SUs) and a plurality of secondary SUs within a dispersedor distributed storage network (DSN), wherein the read request includesa read extra request that specifies at least one of more than a readthreshold number of EDSs from the plurality of primary SUs orinstruction to a SU of the plurality of primary SUs to forward the readrequest to at least one SU of the plurality of secondary SUs, whereinsets of EDSs of the data object are distributedly stored within theplurality of primary SUs and the plurality of secondary SUs within theDSN, wherein the data object is segmented into a plurality of datasegments, wherein a data segment of the plurality of data segments isdispersed error encoded in accordance with dispersed error encodingparameters to produce the set of EDSs, wherein the read threshold numberof EDSs provides for reconstruction of the data segment; transmitting,via an interface of the computing device that is configured to interfaceand communicate with the DSN and via the DSN, the read request for theset of EDSs of the data object to the plurality of primary SUs withinthe DSN; and receiving, via the interface and via the DSN, at least theread threshold number of EDSs from the plurality of primary SUs,wherein: the SU of the plurality of primary SUs provides an EDS of theset of EDSs to the computing device via the DSN and via the interfaceafter receipt thereof from a SU of the plurality of secondary SUs basedon at least one of unfavorable comparison of a DSN operationalcharacteristic to an acceptable DSN operational characteristic asdetermined by the SU of the plurality of primary SUs or the EDS of theset of EDSs is unavailable within memory of the SU of the plurality ofprimary SUs.
 15. The method of claim 14 further comprising: comparingthe DSN operational characteristic to the acceptable DSN operationalcharacteristic; and generating the instruction to the SU of theplurality of primary SUs to forward the read request to at least one SUof the plurality of secondary SUs based on unfavorable comparison of theDSN operational characteristic compares to the acceptable DSNoperational characteristic.
 16. The method of claim 14 furthercomprising: receiving, via the interface and via the DSN, the at leastthe read threshold number of EDSs from the plurality of primary SUs,wherein the SU of the plurality of primary SUs provides the EDS of theset of EDSs from the memory of the SU of the plurality of primary SUs tothe computing device via the DSN and via the interface when the EDS ofthe set of EDSs is stored and available within the SU of the pluralityof primary SUs.
 17. The method of claim 14, wherein: the read extrarequest specifies a first number of EDSs that is more than the readthreshold number of EDSs from the plurality of primary SUs based onunfavorable comparison of the DSN operational characteristic to theacceptable DSN operational characteristic as determined by the computingdevice within a first unfavorable comparison range; and the read extrarequest specifies a second number of EDSs that is more than the readthreshold number of EDSs from the plurality of primary SUs based onunfavorable comparison the DSN operational characteristic to theacceptable DSN operational characteristic as determined by the computingdevice within a second unfavorable comparison range.
 18. The method ofclaim 14 further comprising: instructing at least one SU of theplurality of primary SUs to generate at least one redundant EDS based onat least one EDS of the set of EDSs and to transmit the at least oneredundant EDS to the at least one SU of the plurality of secondary SUsfor storage therein based on unfavorable comparison of the DSNoperational characteristic to the acceptable DSN operationalcharacteristic as determined by the computing device.
 19. The method ofclaim 14, wherein: a decode threshold number of EDSs are needed torecover the data segment; a write threshold number of EDSs provides fora successful transfer of the set of EDSs from a first at least onelocation in the DSN to a second at least one location in the DSN; theset of EDSs is of pillar width and includes a pillar number of EDSs;each of the decode threshold number, the read threshold number, and thewrite threshold number is less than the pillar number; and the writethreshold number is greater than or equal to the read threshold numberthat is greater than or equal to the decode threshold number.
 20. Themethod of claim 14, wherein the DSN includes at least one of a wirelesscommunication system, a wire lined communication system, a non-publicintranet system, a public internet system, a local area network (LAN),or a wide area network (WAN).